Released in 1976, the TEAC A-860 was a three-head stereo cassette recorder designed as an unusually comprehensive recording system rather than a conventional domestic tape deck. Its substantial upright cabinet combined a three-motor transport, separate recording and playback heads, a four-channel microphone and line mixer, switchable Dolby B and dbx Type II noise reduction, variable bias and equalisation controls, peak and VU metering, memory transport functions and extensive source-routing facilities.
The TEAC A-860 was built around a four-track, two-channel stereo cassette format operating at 4.76cm/s. It accepted C-60 and C-90 compact cassettes and supported standard ferric, chromium dioxide and ferri-chrome tape formulations. Its recording controls allowed the operator to match the machine to different tape characteristics through independently adjustable bias and equalisation settings rather than relying exclusively on fixed factory positions.
A true three-head arrangement provided separate erase, recording and playback heads. This allowed the incoming programme to be monitored from the source or directly from the tape while recording remained in progress. The operator could therefore compare the original input with the recorded result immediately, making it possible to identify level, bias or equalisation problems before completing the session.
The transport used three motors. A phase-locked-loop servo-controlled DC coreless capstan motor drove the dual-capstan mechanism, while two additional DC coreless motors operated the supply and take-up reels. Separating capstan and reel-drive duties reduced the mechanical interaction between tape-speed regulation and reel torque. The dual-capstan arrangement controlled the tape on both sides of the head assembly, maintaining stable tape tension through the recording and playback area. Combined with the servo-regulated coreless motor, this produced a specified wow and flutter figure of 0.04% NAB weighted.
The TEAC A-860 included logic-controlled transport operation with separate play, record, pause, stop, fast-forward and rewind functions. The controls allowed the machine to change operating modes without depending on direct mechanical levers, while the transport system incorporated automatic stopping at the end of the tape. A pitch control provided approximately ±4% variation in tape speed. This facility could be used to adjust playback pitch or compensate for recordings made on machines running slightly above or below the nominal cassette speed. The pitch control was intended for playback and did not affect the deck during normal recording.
The transport also incorporated a four-digit electronic tape counter and a programmable memory system. By setting the counter to 0000 and selecting the appropriate memory mode, the operator could arrange for the deck to stop when rewinding to the marked position. The system could also play a tape to its end, rewind automatically to 0000 and then either stop or begin playback again. Memory stop returned the tape to the selected counter position and halted the transport. Memory play returned the tape to the stored position and automatically entered playback. Counter repeat allowed a selected section to be replayed through repeated rewind and playback operation.
The TEAC A-860 provided a four-channel input section designed for microphones, line-level equipment or a combination of both. Four microphone sockets were located on the front panel, while four line inputs were provided on the rear. Each input channel could be switched between microphone and line operation. Individual rotary controls set the input level for each channel. Pan controls positioned the four input sources within the stereo recording field, allowing several microphones or external devices to be combined into a two-channel stereo mix. A master recording control adjusted the overall level after the individual channels had been balanced.
The microphone inputs included attenuation facilities to accommodate sources producing higher output levels. The manual specified a microphone input sensitivity of 0.25mV, with a nominal input impedance of 600Ω or greater. The four line inputs required a minimum level of 60mV and presented an impedance of 50kΩ. A separate front-panel test-tone input accepted an 80mV signal. The machine also incorporated internal calibration facilities that could be used with its meters and adjustable recording controls to establish appropriate bias, equalisation and recording-level settings for the tape in use.
The bias section provided separate control over the recording bias supplied to the tape. Bias adjustment influenced high-frequency response, distortion and maximum recording level, allowing the deck to be matched more closely to the magnetic characteristics of individual cassette formulations. Recording equalisation could also be adjusted separately. The combined bias and equalisation facilities allowed the operator to optimise frequency response and recording behaviour for standard ferric, chromium dioxide and ferri-chrome tapes. A chart in the manual supplied suggested switch positions for a range of contemporary cassette brands and formulations.
The deck incorporated switchable limiting for controlling excessive signal peaks. When engaged, the limiter reduced the possibility of brief high-level transients overloading the tape. The limiter could be used during live recording or with sources containing unpredictable peaks. Recording and playback levels were displayed by two large analogue meters. These could be switched between conventional VU indication and peak-programme operation. VU mode showed average programme level, while peak mode provided faster response to short-duration signal peaks that might otherwise cause tape saturation.
The source and tape monitor selector formed an important part of the three-head system. In source mode, the meters and outputs monitored the signal entering the recording amplifiers. In tape mode, they monitored the signal reproduced by the playback head immediately after it had been recorded. The TEAC A-860 incorporated both Dolby B and dbx Type II noise-reduction systems. Each could be selected according to the recording requirements, but they were intended to be used independently rather than together. Recordings made with either system required the same system to be selected during playback.
Dolby B noise reduction reduced audible tape hiss by applying frequency-dependent compression during recording and complementary expansion during playback. The greatest noise reduction was applied to low-level high-frequency signals, where cassette-tape hiss was most noticeable. The deck included a switchable FM multiplex filter for recording stereo radio broadcasts with Dolby noise reduction. The filter removed the 19kHz FM pilot signal and related subcarrier components that could interfere with the operation of the Dolby circuitry.
The dbx Type II system provided substantially greater noise reduction and dynamic-range expansion. During recording, the incoming signal was compressed before being placed on tape. During playback, complementary expansion restored the original programme dynamics while reducing tape noise. The TEAC A-860 used an RMS level-sensing circuit within the dbx system. This monitored the programme signal and controlled the voltage-controlled amplifier used for compression and expansion. Pre-emphasis and de-emphasis networks, weighting filters and level-sensing circuits were incorporated to adapt the dbx process to the operating characteristics of cassette tape.
With dbx engaged, the specified signal-to-noise ratio could reach up to 90dB. The system also reduced the audibility of modulation noise and other tape-related noise components, allowing lower-level material to be recorded without being masked by the cassette medium’s background hiss. The source-routing section allowed several different recording arrangements. Normal programme sources could be recorded without noise reduction, with Dolby B or with dbx Type II. FM broadcasts could be recorded through the multiplex filter, while previously encoded Dolby or dbx sources could be copied without being decoded and re-encoded.
The TEAC A-860 could also decode Dolby-encoded material while recording the decoded signal without noise reduction. Alternatively, an incoming source could be routed directly to the outputs while a different signal was being recorded, depending on the source, monitor and noise-reduction switch settings. Separate line and headphone output controls were provided. This allowed the rear-panel line output level to be adjusted independently of headphone monitoring. The stereo headphone connection delivered 1mW into an 8Ω load.
The line outputs provided a nominal level of 0.3V into a load of 50kΩ or greater. The rear panel also carried connections for external source equipment and an optional TEAC RC-170 remote-control unit. Timer standby operation allowed the deck to be prepared for automatic recording or playback when used with a suitable external timer. The required operating mode could be selected in advance so that the transport began when mains power was applied.
The large front panel arranged the machine much like a compact recording console. The transport and cassette compartment occupied the upper section, while the lower panel contained the four-channel mixer, bias and equalisation switches, monitoring controls, noise-reduction selectors, limiter, pitch control and master level faders. Its cabinet dimensions and 18kg weight reflected the scale of the mechanical and electronic construction. The TEAC A-860 was considerably larger and more complex than a typical cassette recorder, combining functions that would ordinarily have required a separate mixer, recorder and noise-reduction equipment.
The TEAC A-860 represented an early attempt to turn the compact cassette into a serious production and recording medium. Its three-head monitoring, three-motor dual-capstan transport, four-channel mixer, adjustable tape calibration and dual noise-reduction systems gave it a level of operational flexibility rarely found in cassette equipment of its period.
Features
- Three-head stereo cassette recording and playback system
- Separate erase, recording and playback heads
- Three-motor transport
- Phase-locked-loop servo-controlled DC coreless capstan motor
- Two DC coreless reel motors
- Dual-capstan tape drive
- Four-channel microphone and line mixer
- Four front-panel microphone inputs
- Four rear-panel line inputs
- Individual input-level controls
- Individual pan controls
- Master recording-level control
- Adjustable recording bias
- Adjustable recording equalisation
- Standard ferric, chromium dioxide and ferri-chrome tape compatibility
- Dolby B noise reduction
- dbx Type II noise reduction
- Switchable FM multiplex filter
- Switchable recording limiter
- Source and tape monitoring
- Direct off-tape monitoring during recording
- Switchable VU and peak-programme meters
- Four-digit electronic tape counter
- Memory stop function
- Memory play function
- Counter repeat function
- Variable pitch control
- Timer recording and playback standby
- Independent line and headphone output controls
- Optional RC-170 remote-control compatibility